Lash adjuster assemblies have been employed for many years for reducing noise and back-lash associated with the operation of combustion engine cylinder valve members. Such assemblies generally provide a cyclically pressurized fluid interface at some point in the linking mechanism (drive train) operating the valve members to provide smoother operation and to reduce noise and back-lash as they operate cyclically in conjunction with the valve piston members.
Generally, the term "lash adjuster" as used herein denotes two different types of which one features a plunger member moveable in response to cyclical pressurization of fluid for operation of the valve member by reciprocal movement of a body member of the assembly reciprocated by rotation of a cam member driven by the engine and the other, commonly called "tappet assembly", wherein the body member is held in a relatively stationary condition and the cam member drives the plunger member cyclically rather than the body member.
Both types generally feature an internal chamber within the plunger member for providing a resevoir of fluid of which a portion is cyclically pressurized by the reciprocal movement of the plunger member with the resevoir being in fluid communication with a source of fluid commonly located in the engine block outside of the body member by means of fluid passageways through respective walls of the plunger member and the body member.
Fluid operated lash adjuster assemblies of interest to the present invention are of the type wherein the capacity of the resevoir within the plunger member is limited by the height of the fluid passageway by which fluid is able to enter the plunger member chamber containing the resevoir of fluid.
Although some lash adjusters feature a fluid passageway into the plunger member resevoir chamber that is adjacent the upper-most height of the chamber such as disclosed in U.S. Pat. Nos. 2,737,934; 2,815,740; 4,361,120 and U.S. Reissue Pat. No. 24,506, the disclosures of which are incorporated herein by reference, others, such as disclosed in U.S. Pat. No. 3,025,842, the disclosure of which is incorporated herein by reference, do not, but rather feature a fluid passageway entrance into the plunger member chamber that is substantially lower than the actual vertical height of the chamber which limits the resevoir capacity within the chamber.
It is to the latter type of lash adjuster assemblies to which the present invention is addressed, i.e. those lash adjusters assemblies for which the height of the fluid resevoir within the plunger member chamber is less than the height of the chamber by reason of the location of the fluid passageway entry location into the chamber which necessarily limits the resevoir capacity which, in turn, may lead to insufficient fluid source for proper operation particularly on start-up after the engine has been idle for extended periods of time.